A hard problem

Question

The cost to rent a 200 square foot storage unit is $60 per month. The cost to rent a unit that is 325 square feet is $160 per month. Write an equation to represent the cost to rent a unit that is X square feet of storage space.

Answer 1

It appears that you only have two points, so we'll make the assumption that this will be a linear equation...as a linear equation it should have the following form:  y=mx+b, where m=slope and b is the y-intercept.

 

It may help you to graph the two points to visualize the linear relationship.  Plot the square footage as the independent variable (x-axis) and the cost as the dependent variable (y-axis).

 

m (slope) = rise/run = (y2-y1)/(x2-x1) = (160-60)/(325-200)=100/125=4/5

 

Select one data point and the slope that was just calculated and put it into the slope/intercept formula and solve for b (the y-intercept)

 

y=mx+b --> 60=(4/5)(200)+b --> 60=160+b --> b=-100

 

Now that you have m and b, you can rewrite the original equation:  y=(4/5)x-100

 

B/R John